Jiangtang Xiaoke granule attenuates glucose metabolism disorder via regulating endoplasmic reticulum stress in the liver of type 2 diabetes mellitus mice

Abstract

OBJECTIVE

To observe the effect of Jiangtang Xiaoke (JTXK) granule on endoplasmic reticulum (ER) stress in high fat diet (HFD)-induced type 2 diabetes mellitus (T2DM) KK-Ay mice.

METHODS

KK-Ay mice were fed with HFD to induce the T2DM model, while normal control C57BL/6J mice were given standard feed. Fasting blood glucose (FBG) in all mice was measured weekly and oral glucose tolerance tests (OGTTs) were performed at 4 and 10 weeks after start of treatment to determine glucose metabolism. Serum fasting insulin (FINS) and insulin sensitivity index (ISI) were measured to determine insulin sensitivity. mRNA expressions of eukaryotic initiation factor-2 alpha (eIF2α), glucose regulated protein 78 (GRP78), activating transcription factor 4 (ATF4), and C/EBP homology protein (CHOP) were assessed by reverse transcription polymerase chain reaction and the protein expressions of p-eIF2α, GRP78, and CHOP were assessed by Western blotting.

RESULTS

JTXK granule significantly reduced FBG and free fatty acid levels and improved OGTT at the 120 min of the 10-week treatment in T2DM KK-Ay mice. FINS and HbAlc levels were reduced and insulin sensitivities were increased in KK-Ay diabetic mice, which were improved with the treatment of JTXK granule, especially at the 7 and 3.5 g/kg doses. JTXK granule at the 3.5 g/kg dose was most effective in reducing both gene and protein expressions of eIF2α, GRP78, and CHOP.

CONCLUSION

ER stress response is increased in T2DM KK-Ay mice. Treatment with JTXK granule attenuates glucose disorders, improves insulin sensitivity, and reduces serum FFA in T2DM KK-Ay mice. The mechanisms may be attributed to regulation of the signaling ER stress pathway via decreasing eIF2α phosphorylation and suppressing eIF2α-ATF4-CHOP activation.